1. Field of the Invention
The invention relates to a method and a device for the production of a container with an opening, whose opening axis is at an angle to the container axis. In the method, a blank is introduced into a blow mold, and the container component of the blank is molded in the blow mold by means of blowing. A blow mold has in a blow mold body a blow mold cavity corresponding to the outer shape of the container, and a stop zone for a fixing region on a blank that can be inserted into the blow mold. In addition to such a blow mold, a blowing device also requires a blowing nozzle that can be sealed on the blank. Additionally, such blowing devices usually have a stretching pin for the stretching of the blank.
2. Discussion of Related Art
Bottles and containers blown with plastic blanks usually have an opening, the axis of which coincides with the container axis, or is arranged parallel to it. The blank is inserted into the opening being arranged orthogonal to the blow mold body into the blow mold cavity using tongs, and contacts the blow mold with a fixing region in the neck area. The insertion direction of the blank is parallel to the blowing mold axis. The walls of a container part of the blank are thereby positioned at a distance to the limitation of the blow mold cavity being approximate equal around the perimeter. The fixing region is now pressed using the blowing nozzles, and the blank is blown until the plastic walls have the shape of the blow mold cavity. Further in most cases a stretching pin is inserted into the blank, and the blank is stretched with it in the direction of its container axis. Practically at the same time, the blank is blown, and by that the material of the blank walls is stretched.
If it should be departed from the rule of the coincidence of the opening axis and the container axis, irregularities in the wall thickness are to be expected due to varying stretching conditions in the different areas of the blank walls. In the case of parallel axis, an irregular stretching of the blank walls can be counter-acted upon in narrow limitations, for instance by means of aimed warming of the blank. However, if the opening axis even extends at an angle to the container axis of the blow mold, the distances between the walls of the inserted blank and the limitations of the blow mold cavity vary with increasing distance from the opening. Achieving a nearly equal wall thickness of the finished container seems to be impossible with common rotation symmetric blanks with evenly thick walls and a common blowing method, or a common stretching and blowing method.
A method and a device for mold blowing of a plastic container with an opening axis extending at an angle to the container axis is known from EP-A-0361 141. The container is blown from a blank in a blow mold. For this purpose, the blank is inserted into a blow mold. Its fixing region in the area of the container opening is pressed onto the blow mold by means of a mold piece for the molding of the container""s mouth piece. The mouthpiece is sealed with a blowing piece. A stretching pin extends through the blowing piece into the blank. A streching pin extends through the blowing piece into the blank. The blank can be stretched with the stretching pin. It also has a multitude of air intakes, through which compressed air is pressed into the blank during the blowing of the blank into a container.
The opening axis of the blank and the blow mold are directed vertical, namely parallel to a insertion direction of the blank and to a blow mold axis. In order for the neck axis of the container finally being at an angle to the container axis, a cavity axis of the blow mold cavity corresponding to the container axis is inclined at an angle to the insertion direction and the blow mold body axis, respectively.
In order to avoid a part on the neck area of the container resulting too thin, the container part of the blank is bent in the direction of the cavity axis. This can occur by means of molding the blank in a special mold before inserting it into the blow mold. It can also be deformed inside of the blow mold after insertion by means of a slide, or by means of stretching on a circular path with a curved stretching pin.
All of the suggested variations of the method for the molding of the blank need, besides insertion and blowing, an additional process step. This step increases the production time for a container.
It is therefore known that in a method for the production of a container with an opening, the opening axis of which is at an angle to the container axis, a blank is inserted into a blow mold, a fixing region of the blank is pressed against a stop zone on the blow mold, and the blank is pneumatically molded in the blow mold.
It is therefore the object of the invention to suggest a method and a device, with which it is possible, especially by using common rotation symmetric blanks, to blow a container, the final opening axis of which is arranged at an angle to the container axis. The wall thickness of the finished container shall be nearly constant at a cross section crosswise to the body axis. Particularly, the production time for a container shall be as short as possible.
This object is solved by pressing the fixing region of the blank against a stop zone on the blow mold being inclined at an angle other than 90xc2x0 with respect to the insertion direction of the blank. Thus it is molded right during the insertion and stretching in such a way that an opening axis of the blank is at an angle to the container axis of the blank. By that an additional and production time extending molding step can be eliminated.
The angle between the axes of the blank is coordinated with the angle between the opening axis of the container and the container axis. Due to this, the walls of the container piece of the blank inserted into the blow mold and the blow mold cavity are, independent of the distance to the opening, at an approximate even distance to each other. This allows the use of blanks that are rotation symmetric at least in the container piece.
A container is produced using such a method, which has in particular container walls arranged around a body axis, and a container bottom, and the container bottom of which is usually parallel to a plane extending at an essentially right angle with respect to the container axis. The axis of its opening positioned opposite of the container bottom is at an angle to the body axis. Therefore, such containers, especially tilted neck bottles intended for toilet bowl cleaning, are advantageously produced by blowing in a blowing mold a blank made of thermoplastic plastic material and having walls, a bottom, and a pre-molded opening. A rotation symmetric blank is thereby molded before the blowing of the container piece in such a way that an axis extending through the opening of the molded blank extends at an angle to the symmetry axis of the blank""s walls (container axis). The container axis of a rotation symmetric blank is coincident with the original rotation or symmetry axis of the blank. Preferably, the angle of the opening axis to the symmetry axis of the walls is smaller, or equally large, however especially preferably equally large as the deviation to be achieved of the opening axis to the body axis.
This measure ensures that a rotation symmetric blank can be used, and the walls can have wall thickness deviations coming from the tilting only in the already thicker neck area of the finished container. The finished container has practically no relevant wall thickness deviations in the walls and in the bottom, as with the previously mentioned tilting the walls of the blank are oriented approximately parallel to the wall of the container to be achieved. A difference between the angle of the container part axis to the opening axis of the blank, and the cavity axis to the opening axis of the blow mold cavity, can preferably be up to 6, or in case of low quality requirements, even up to 9 degrees, before the resulting wall thickness deviations effect the quality of the container.
In containers that must be stretched, the stretching direction is appropriately orthogonal to the orientation of the orthogonal and parallel-epipedic body of the blow mold. In order to obtain an opening axis tilted from the body axis, the blank inserted into the blow mold is stretched in a stretching direction that is at an angle to the opening axis. A fixing region designed at the neck of the blank is pressed against a stop zone on the blow mold. The plane of this stop zone is at an inclined angle with respect to the outer surface surrounding the stop zone, or at an inclined angle with respect to the orientation of the essentially prismatic and orthogonal body of the blow mold, and also to a possibly existing stretching direction. For a stretched container the stop zone can be at this angle merely toward the stretching direction. In a non-stretched container, the stop zone is at an angle other than 90xc2x0 to the plane of the outer surface of the blow mold body surrounding the stop zone, or to the blow mold body axis, or to the body axis of the container to be blown, which corresponds to the cavity axis of the blow mold cavity.
Advantageously, the fixing region is pressed against the stop zone using a pressing piece. This pressing piece can be separate from the seal of the blowing nozzle, or advantageously have a seal, and coincide with the blowing nozzle. The pressing operation guarantees the right fit of the blank in the mold. The separation of the pressing piece of the blowing nozzle from a sealing piece arranged around it enables a diagonal pressing, and an orthogonal sealing of the nozzle. Surprisingly, however, it was shown that fewer errors occur in a pressing and sealing in a single step using a single piece.
Corresponding to the method, a blow mold for the production of a container with an opening, the opening axis of which is at an angle to the container axis, has a blow mold cavity in a blow mold body, and a stop zone for a fixing region of a blank able to be inserted into the blow mold. The blow mold cavity corresponds to a container outer shape, and the stop zone is inclined at an angle other than 90xc2x0 with respect to the blow mold body axis. Corresponding to the angle of the opening to be achieved, the blow mold has a stop zone for a fixing region at the blank""s neck, the plane of which extends at an angle other than 90xc2x0 to the outer surface surrounding the stop zone, or an acute angle with respect to the orientation of the prismatic blow mold body deviating from 90xc2x0 according to the angle between the opening axis and the stretching direction or the orientation of the blow mold body. The blow mold cavity corresponds to the finished container exterior form, and this deviation is smaller or equally large as the angle between the opening axis and the body axis of the finished container. The maximum angle between the opening axis and the body axis is within a range of up to 24xc2x0 depending on the design of the opening and the manner of retaining of the tongs inserting the blank into the mold. This blow mold enables the molding of the blank simultaneously with its insertion into the blow mold cavity.
In order to achieve larger angles between the container axis and the opening axis, the cavity axis of the blow mold cavity, which is corresponding to the body axis of the container blown in the blow mold, is advantageously at an angle to the stretching direction and/or to the orientation of the essentially prismatic body of the blow mold. It must be considered, however, that the deviation of the cavity axis from the stretching axis should not be larger than approximately 6 degrees with average bottle proportions. More generally speaking, the maximum deviation of the stretching axis, or of the container axis of the blank from the body axis of the finished container, should not be more than 10 to 15% of the container diameter in deviation direction. Even more generally speaking, the ratio between the largest distances on a line approximately normal to the stretching axis and facing each other of the blow mold cavity to the stretching axis should be less than 2, or more than xc2xd.
Appropriately, stretching occurs by means of a stretching pin. With the stretching along a straight line (straight-line translation of the stretching pin) at an angle to the opening axis through the opening of the blank, this angle is limited by the size of the opening and the diameter of the stretching pin. In order to increase this angle, advantageously the stretching pin has, at least in the direction crosswise to the stretching pin axis, a substantially smaller cross sectional dimension than the opening diameter of the blank. Advantageously, the other cross sectional dimension crosswise to the longitudinal axis of the stretching pin is as large as possible. Alternatively, the blank is stretched by a translation of the stretching pin along a curved path. This enables the use of a stretching pin having the largest possible circular cross section.
The stretching pin can be curved completely or partially. The curve can also have different radiuses. It must subsequently be fed on a path that accommodates this curve. This path can have different radiuses and tilt motions around different points. It must be laid out depending on the position, i.e., the degree of forward movement of the stretching pin, and depending on the mold and the degree of blowing of the container. It must be considered that the stretching pin may not touch either the blank walls, or the opening area of the blank. The path of the tip of the stretching pin must, of course, be positioned completely within the blow mold cavity. Therefore, the path must be adjusted to the container mold. At such a stretching pin not fed at a straight line, however, the opening axis can be at a larger angle to the container axis, than with stretching pins fed at a straight line.
The thermoplastic material preferred for the production of the blank and the container is PET (polyethylene terephtalate). PEN (polyethylene naphtalate) and other plastics are also used.
In a blow mold, the stop zone is oriented diagonal to the blow mold body axis, or to the outer surface of the blow mold body surrounding the stop zone and being oriented orthogonal to the blow mold body. In particular, the blow mold has a stop zone for a fixing region at the neck of the blank, the plane of which is at an acute angle of less than 90xc2x0 to the orientation of the blow mold body, whereby the deviation of the right angle is smaller than the angle between the opening axis and the container axis of the finished container, or corresponds to this angle. The blow mold cavity has a diagonal neck axis. If on a blowing device with such a blow mold a device for the stretching of the blank is provided such as a stretching pin, the stretching direction is at an angle to the opening axis of the blow mold cavity. The plane of the stop zone is arranged at an inclined angle to the stretching direction, i.e., to the translation direction of a stretching pin being pushed along a straight line. This enables the direct blowing of so-called tilted neck bottles from a blank with rotation symmetric walls in a blow mold, and with a straight stretching pin. The blank""s walls are stretched approximately centric into the blow mold cavity by the stretching pin that has been inserted into the blank at an angle to the opening axis.
Appropriately, the blowing nozzle has a movable interior piece for pressing the blank onto the stop zone, and, movable relative to this, an exterior sealing piece for the sealing of the nozzle to the blow mold body. Thus the pressing function and the sealing function can be performed separately, and successively. In particular, the pressing can occur on another plane than the sealing. Both of these planes can be at an inclined angle to each other. Preferably, however, the blowing nozzle is equipped with a seal, and seals the opening edge of the blank.
In a further developed advantageous embodiment, the longitudinal axis of the blow mold cavity is at an angle to the stretching direction and/or to the orientation of the blow mold body and its blow mold body axis. This enables the longitudinal axis of the blow mold cavity being at an angle to the opening axis that is larger than the angle between the opening axis of the blank and the container axis, or stretching axis. This way, larger angles between the opening axis and the body axis of the container are possible.
In a blowing device with a blow mold and means for inducing positive pressure into the blank, a transport device for the insertion or removal of a blank are also intended. A blow mold with a blank with rotation symmetric walls inserted into the blow mold is, according to the invention, characterized in that the container axis of the container piece of the blank is at an angle to the opening axis of a finished container""s outer shape corresponding to the blow mold cavity. Simultaneously, the opening axis can extend at an angle to a longitudinal axis of a stretching pin movable along this longitudinal axis, namely when a fixing region of the blank provided around the opening abuts to the blow mold, or is pressed against the stop zone. The entire blank still has a rotation symmetric shape during the insertion. The opening axis is initially directed parallel to the stretching pin""s longitudinal axis until the stretching pin is inserted into the blank so far that its container piece is fixed in its position by the stretching pin. Once the stretching pin is inserted into the blank, and the container area is thereby positioned and fixed in the direction, the fixing region of the blank is advantageously pressed against the blow mold by means of a pressing piece. The opening axis is tilted wit respect to the container axis by the stretching and pressing operation. Initially, one-sided pressure is exerted onto the fixing region, and the opening axis is thereby bent. When the fixing region abuts to the stop zone, the pressing piece symmetrically abuts to the blank. The stretching and pressing advantageously occurs synchronous up to that moment, in which the pressing piece presses the fixing region firmly onto the stop zone. Subsequently, the stretching operation is continued without interruption, and the blank is blown simultaneously. Axial shaped, rotation symmetric blanks with even wall thicknesses can be used for the inventive method.